While I love the suggestions in the thread about unit balance, I also think we need more radical game changes to make war between empires more fun and more balanced. These ideas are about empire-to-empire war rather than about a single battle over a planet.

I think there are a few tenets to keep in mind:

1. Good strategy should be a force multiplier.
2. Wars should (in general) not be decided quickly, giving defending player a chance to react.
3. It should be easier to defend than to attack.

I don't think any of these three is true today. Here are some ideas to implement them:

JUMPSHIPSThis post makes some excellent suggestions about jumpships. In general, I agree with it. If jumpships had limited range, then it would be harder to surprise an empire. This alone would probably help all three tenets.

There are a few tweaks to consider. Instead of a range based on where the fleet was deployed, perhaps any fleet just has a limited amount of "jumpfuel" available (or whatever). Jumpfuel can only be replenished at jumpship bases. Fire & Movement doctrine might have mobile jumpship bases which would serve as jumpship carriers for strikes deep into enemy territory. But of course, the mobile bases would move at starship speed.

The advantage of using jumpfuel is that it is easier to manage when fleets split and rejoin (because we just split/rejoin the fuel as well).

An alternative (and possibly better) mechanic is to introduce the concept of "jump beacons". Jumpships may only jump to within a certain range of a jump beacon. All jumpship bases (and capitals in F&M doctrine) are jump beacons. In addition, mobile jumpship bases serve as beacons. Perhaps the player can even build beacons in open space. This is very similar to WTVd0's original idea, but eliminates the binding between a fleet and its base.

MOBILIZATION
Wars between empires are often just a series of disconnected planetary battles. We need more ways in which being part of an empire helps a planet to defend itself. One idea is the concept of "mobilization". At any point in time, a player should be able to move a certain number of ground units automatically from planet to planet via normal trade routes. Moreover, when an enemy fleet attacks a world, ground units should automatically mobilize from neighboring worlds to help defend. Units would automatically move as soon as an enemy fleet is detected.

The rate of movement can depend on various factors: existing trade routes, designations (Citadels and capitals would get more troops). Certain structures could improve (or hinder) mobilization.

We could extend mobilization to ships (perhaps at the player's option) and also introduce mobile units that act as planetary defenses. For example, we could introduce mobile HEL cannons (or something).

AREA DENIAL
If an enemy empire can attack any world in your empire, then you have to defend every world. But there are more interesting strategic possibilities if some worlds are more protected than others. Ideally, it should be harder for an enemy to attack inner worlds than peripheral worlds. We need to introduce some area denial mechanics that limit enemy movement.

Citadels are a start. They are designed to defend worlds around them, though they could use a buff. We should introduce similar means of defending the borders of an empire.

Constructions like minefields and interdictors (jump disruptors) would work for this. In some scenarios we might use natural features such as rift zones and nebulae to limit movement.

These ideas are just a start. I'm not sure which would work or not. If you've got your own ideas, please post them as responses here.

Those are awesome George, this is all just awesome, serious game changers. Here are few of my own suggestions if these things are really getting underway:

Perhaps I do not want to expand my empire in a war, I just want to knock you out or a few sectors, there should be a way to invade and destroy empires without auto-capture of the world. Either an "abandon world" button after capture or "invade w/o conquer" button on the attack menu.

Citadels should auto-fire on enemy ships within range intrajump (i.e., not on world). However, with all these auto movements of troops and firing missiles, we would need need need a way to designate allies and enemies.

I propose limiting fleets that CAN enter the rift nebula's to be penalized to 1/25th speed of normal jump range (but retain radar) or heavily minimize the amount of passages through the rift zones. No one was using Starship/cruisers/whatever toward the end, so the rift zones as decent protective barriers were nullified. Also, the ability to travel extra-galactic.... annoying, though amusing.

::Home World::
Perhaps, Home world Capitals could be equipped with an upgraded version of jumpmissiles that come w/ your home world. Wouldn't it make sense that a home world would have extra abilities? Also, would we be able to limit a conquer to if you loose your Home World your empire dies slowly.
Like this.. You get one Home World and the only way to kill the empire is to take the Home World, no more chasing that sucker across the galaxy while other empires SC spam you making it near impossible to conquer them. Give the Home World extra abilities like jumpmissiles and ++ground troop production and +++world defenses. If you do loose your Home World the empire dies a slow death, this gives you the ability to retake it, but if you don't retake in time you die, also gives the added benefit if you are out for annihilation then all you have to do is take and defend the captured Home World. With all the extra world defenses/mines/troop transporting intraworld, Home World conquering would not actually be the easiest method to conquer an empire.

Perhaps this would encourage limited wars and discourage the scourge wars (total war of annihilation) we have become accustomed to but aren't actually that fun. It seems that if you want to fight a war right now it grows fanatically into a scourge war which actually has come to discourage war altogether. War should be about annihilation and defeat, but also about posturing. You can't posture for power if every war threatens your hard worked on empire that took months to create. Conquering an empire should be the most difficult aspect of the game.

Just my two cents. Thanks always for the amazing game George, and also to everyone else who is helping out sooooooo much. You guys are great.

A few thoughts about beacons to consider if you decide to implement them:

How will mixed fleets of jumpships and starships be handled under the beacon model? Can they still be put in fleets together? Can a mixed fleet move around outside of a beacon's range? If so, what happens to the jumpships if the fleet splits or if the starships are lost to attrition but there are still jumpships remaining in the fleet? (These questions are also applicable under the fuel model.)

What happens to jumpships in range of a beacon when the beacon or beacon-world is captured? Are they rendered immobile? Can they move at gunship or starship speed of their own? Can they jump back into range of another beacon? What happens to fleets in transit when a beacon is captured or destroyed?

Can jumpships jump between active beacons' ranges through space that is not controlled by a beacon? If not, what happens in situations where beacon ranges intersect but the most direct jumpship path is through space that isn't covered by a beacon?

Do beacons associated with jumpship yards come online as soon as the yard is designated? Do they have an activation time (similar to the administration structure on a sector capital)? Are they discrete structures or intrinsic to the jumpship yard designation? If a jumpship yard is captured, is the beacon captured with it or is it destroyed and has to be reactivated? (Perhaps the beacon is buried deep beneath the planet's crust and must be exhumed before it will stops working for the civilization that built it, with exhumation time depending on infantry stationed on the planet or something like that.) Is beacon range fixed or does it vary with planetary TL? Does operating a beacon consume resources? Can beacon structures be manually built on other world classes, like sector capitals and citadels? If so, do they consume resources?

Beacons that are constructions in open space are an interesting thought. Do they build their own defenses by importing resources through trade routes, like outposts and other constructions in classic Anacreon? Can they be captured? Are they attacked via space bombardment, through infantry attack, or both? If constructions like beacons can participate in space combat, do fleets orbit around them (which doesn't make much sense from a physics perspective) or does there need to be some other model for combat? Do they have to be in range of a sector capital? If not, what will prevent empires from spamming them everywhere to get comprehensive jumpfleet coverage?

Will warp transports be introduced to allow players to colonize distant regions of space, beyond jumptransport range, and to conduct military operations in regions where they don't have jump infrastructure?

How about some kind of "stargate" world designation which allows any ship to travel between other "stargate" worlds? Then at higher tech levels (say TL9?) we could upgrade it to a "super-stargate" which allows instant travel to any friendly world in the galaxy. Something like the farcasters in the novel Hyperion. This is in addition to having jumpfuel, so players are encouraged to designate stargates if they want to increase their jumpfleet's projection power...

How about some kind of "stargate" world designation which allows any ship to travel between other "stargate" worlds? Then at higher tech levels (say TL9?) we could upgrade it to a "super-stargate" which allows instant travel to any friendly world in the galaxy. Something like the farcasters in the novel Hyperion. This is in addition to having jumpfuel, so players are encouraged to designate stargates if they want to increase their jumpfleet's projection power...

You pretty much described exactly how warp links and gates worked in the older editions.

Warp links are giant super-gravity generators that literally bend and break space-time. A warp link is constructed in such a way that a fleet entering one is able to exit a short time later at another warp link, possibly on the other side of the galaxy. In practice, a net­work of warp links could connect an entire empire so that warpfleets from any region can travel to any other region in years instead of decades.

Gates are warp links that do not need a receiving link - you could warp ships anywhere in the galaxy. In turn, empires can prevent gating fleets by building disruptors.

I'm not sure if gate technology would be good for game balance - its already impossibly hard to face a mature empire.

Project Renegade (Beta) : "The Poor Man's Corporate Command!"
"Cowards die many times before their deaths; The valiant never taste of death but once. " -Julius Caesar as written by William Shakespeare, a notorious permadeath player.

Is there any chance transports could start in a height that is out of range of defences stationed on a planet?
If my fleet attacks a planet, and the planet has ships stationed on it, not a fleet in orbit, the defending ships are able to wipe out an entire fleet, thousands of transports, before my attacking ships can even get down into range of those defending ships. In general, any attack of planet stationed defences should not start in range of those defences.